Quantitative knowledge of the gravitoinertial environment is critical to many materials processing, fluids physics, and biotechnology space experiments. The need for high-quality three dimensional acceleration measurement is increasing on Space Shuttle missions, for example. The challenge for space experiment support is to provide access to acceleration data and produce data products which are useful to microgravity experimenters. Making accelerometer measurements as part of space flight experiments is not as straight forward as recording a simple time series of triaxial accelerations for flight investigators. In order to be useful, many experiments require the derivation of information from acceleration data in condensed and accessible forms.
The detection of large acceleration events due to external gravitoinertial disturbances, the frequency distribution of these disturbance events, and their data representation are key parameters of interest in materials processing applications. Gravitoinertial disturbances due to crew motion effects (e.g., treadmill activity, payload interaction, etc.) and mechanical anomalies such as the cycling of fans and pumps can have a significant impact on the growth of uniform crystalline structures, for example.
The microgravity environment refers to the forces experienced by a unit mass at a specific location on a space vehicle. There are two components of acceleration that make up the microgravity environment. One class of accelerations is called slowly varying or quasi-steady-state accelerations. These are also frequently referred to as "background" accelerations, and sources include gravity gradients, aerodynamic drag, and low-frequency spacecraft rotation.
A second class of accelerations is known as oscillating or transient accelerations. These are frequently referred to a "g-jitter" and represent time-varying accelerations that result from such factors as crew activity, propulsion and attitude control systems, experiment operations, and communications. In normal low earth orbit operations, the g-jitter component dominates the background acceleration environment in an orbiting craft and is believed to have the greatest impact on many materials processes.
Under normal Earth gravity conditions, buoyancy effects (lower density material rises, higher density material falls) can create significant convection and phase separation in the liquid state that are known to create imperfections and nonuniformities in certain materials. In the microgravity environment of space, this natural convective mixing and separation of materials of differing density is greatly suppressed, allowing for the production of novel materials that cannot be manufactured on the ground. In addition, microgravity scientists are better able to investigate subtle effects such as diffusion-controlled mixing or surface tension gradient induced mixing (known as Marangoni flow) that are normally masked on Earth by the larger, dominating buoyancy convection mixing effect.
Examples of how this unique environment is being used include growth of larger, more perfect semiconductor crystals for advanced electronics applications; production of light weight, unique 2 -phase composite materials that cannot be produced on Earth; and growth of larger protein crystals from which detailed structural information can be obtained that might prove useful in the production of future disease-fighting drugs.
As these applications mature and as other applications are discovered, there will be a growing need to measure and quantify the exact microgravity conditions under which experiments are performed. The present invention was particularly designed and developed to support scientists who require detailed information on the microgravity environment in space.